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So long as humanity is limited to throwing high velocity gas oot the back of rockets to get around the solar system, we’ll be limited by access to volatile mate

So long as humanity is limited to throwing high velocity gas oot the back of rockets to get around the solar system, we’ll be limited by access to volatile material. Spacex is betting on CH4 and oxygen, nuclear rocket designs (NERVA) used hydrogen, although they could use pretty much anything. Earth is in a peculiar position such that the delta V of getting to orbit will also get you to anywhere else in the solar system fairly quickly. So if launch to LEO is cheap, fuel will be a large proportion of cargo imo. Note solar sails and some other propulsionless designs negate this requirement.

mavhc 5y ago
Starship aims for $10/kg, and a 1U cubesat is about 1kg
rbanffy 5y ago
> fairly quickly. The delta-v maps show the minimum needed to get from one place to the other. In order to get from one place to another more quickly, you’ll need larger delta-v’s at the ends of the trip. Even though the rest of the solar system is within reach, we don’t want to send humans to Pluto and back on 20-year missions.
- Invictus0 5y ago
  you mustn't be afraid to dream a little bigger darling. I can definitely imagine a mission to pluto and back.
  - Loughla 5y ago
    A 20 year mission to Pluto would be unsuccessful without cryogenic or otherwise science-magical-sleep system. I cannot imagine a single set of humans who could spend 20 years together, without any way to leave the small space of a ship, and not absolutely lose their minds. That long of a trip means we just end up sending absolute lunatics and/or small pieces of chopped up lunatics after the inevitable murders.
    - tsimionescu 5y ago
      Not to mention, it's extremely doubtful that a human body could survive anywhere close to 20 years in space.
      - rbanffy 5y ago
        The ship would need to be very large - artificial gravity and adequate shielding for radiation and impacts would need to be provided, as well as an insane amount of redundancy and survivable abort routes. Attempting to do it with technologies we have, even with infinite funding, would be next to impossible without incurring in unacceptable risks.
  - rbanffy 5y ago
    I can too, but we’ll need much better engines than what we have now to get there and back in an amount of time a crew can function. Sending 20 years worth of consumables and spares is complicated, as well as the moral questions about sending people on 20 year missions.
    - avmich 5y ago
      For some time an assumption - a rule of thumb of a sort - was that chemical rockets can get people comfortably around within Mars orbit, and to get further away we need something better. That "something" is likely not solid-phase nuclear engines, with Isp about twice as good as LOX/LH2, and probably not gas phase nuclear engines... but thermonuclear engines, which get closer to feasibility with advances in thermonuclear energy field. A thermonuclear engine could be more attainable than a thermonuclear electrical plant, and cheaper LEO access could be a big part of enabling technology. Having engines like that we may talk about much faster trips to Pluto and back.
      - rbanffy 5y ago
        > A thermonuclear engine could be more attainable than a thermonuclear electrical plant Very true. Nobody cares about breakeven for that use case.
jillesvangurp 5y ago
There are alternate sources of propellant in the solar system. Lifting it out of Earths gravity well is relatively expensive. But once you have enough of it, you could start transporting propellant from elsewhere in the solar system and start stockpiling it in strategic orbits around various objects in the solar system. Once you can do that, you'd minimize the launch weight from earth to be able to get to a LEO fueling point and use the weight savings for more interesting cargo. One industry that could emerge quickly is that of asteroid mining. There are plenty of interesting asteroids with precious metals, water, and other resources. Right now the cost of getting to these asteroids, mining them, and transporting the mined goods back is so expensive in delta-v that it has not been done yet despite several companies having been active planning for this for quite some time. So, SpaceX getting their star ship going might be a big deal.That enables us getting stuff into space and that enables us bootstrapping mining and construction activity in orbit. Plenty of science fiction books have been written on this. There's no shortage of ideas here.
- BurningFrog 5y ago
  My big fear with asteroid mining is that if you can move an asteroid to Earth orbit, you can also smash it into any capital city or military base on Earth. Which means that this capability is a weapon more powerful than even nuclear missiles! I don't think the world will let this be run on the honor system. So I expect space travel to become extremely tightly controlled once we get close to this tech level.
  - 0xffff2 5y ago
    A relatively small number of nuclear missiles is enough to wipe out human civilization. There's no such thing as "a weapon more powerful than even nuclear missiles" in terms of Earth-focused weaponry. And we've done very little if anything to prevent countries from acquiring and maintaining nuclear missiles. If we let North Korea have nukes, what makes you think we would try to stop countries from developing space capabilities?
    - gary_0 5y ago
api 5y ago
> Earth is in a peculiar position such that the delta V of getting to orbit will also get you to anywhere else in the solar system fairly quickly. Tangent: One of my favorite answers to the Fermi paradox (not mutually exclusive with others) is that much of the life in the universe is stuck at the bottom of huge gravity wells ("super Earths") that make space flight immensely difficult and expensive, making the development of a space industry far less likely. It's a variant of the rare Earth hypothesis. Not only might Earth be rare for its stability and long-lived biosphere but also for the fact that it's large enough to hold onto a thick atmosphere and water but not so large that you can't get off it with relatively benign (compared to higher energy alternatives) chemical propellants. Increases in the mass of Earth would make space launch exponentially not linearly harder. Getting anything non-trivial off a super-Earth would probably require nuclear or hybrid (e.g. LANTR) rockets, which are problematic for ground launch in a biosphere. They'd also be a lot more costly.
Retric 5y ago
NERVA or other Nuclear thermal rockets are actually fairly low ISP compared to ION drives. A solar panel + inert gas gets you anywhere in the solar system. The real issue is what’s the point? The economics of asteroid mining gets much worse if you consider bringing vast quantities of say gold back to earth would tank the value of gold.
- im3w1l 5y ago
  I have been thinking about this and what I really hope we do is build a fully automated colony in space. Making it livable for humans is a huge pain in the ass, but if we restrict the scope to just sustaining robots then it becomes easier. Energy is easy: Solar panels. There is also repairs which might be trickier. Need to mine for materials and refine them into spare parts. Once you have a self-sustaining colony you could use it to assemble useful stuff. Luxury goods for terrestrial consumption. Or you could use it to build a stage-2 colony that is suitable for humans. Or maybe rockets and stuff to keep expanding into space.
  - jcims 5y ago
    Pretty interesting Lex Fridman podcast episode in this area: https://youtu.be/KW8Vjs84Fxg https://youtu.be/KW8Vjs84Fxg It’s light on technical details but it’s encouraging to hear that there is progress being made in this direction.
- BurningFrog 5y ago
  Gold is a special case, but tanking the price of expensive metals is exactly the point of asteroid mining. If prices for nickel, iron, copper, platinum, etc were cut by 99%, it would raise human living standards ENORMOUSLY.
  - skykooler 5y ago
    It would be nice if people stopped stealing catalytic converters because the plantinum, palladium etc were no longer worth the effort.
  - 5y ago

mavhc 5y ago

Starship aims for $10/kg, and a 1U cubesat is about 1kg

rbanffy 5y ago

> fairly quickly. The delta-v maps show the minimum needed to get from one place to the other. In order to get from one place to another more quickly, you’ll need larger delta-v’s at the ends of the trip. Even though the rest of the solar system is within reach, we don’t want to send humans to Pluto and back on 20-year missions.

Invictus0 5y ago
you mustn't be afraid to dream a little bigger darling. I can definitely imagine a mission to pluto and back.
- Loughla 5y ago
  A 20 year mission to Pluto would be unsuccessful without cryogenic or otherwise science-magical-sleep system. I cannot imagine a single set of humans who could spend 20 years together, without any way to leave the small space of a ship, and not absolutely lose their minds. That long of a trip means we just end up sending absolute lunatics and/or small pieces of chopped up lunatics after the inevitable murders.
  - tsimionescu 5y ago
    Not to mention, it's extremely doubtful that a human body could survive anywhere close to 20 years in space.
    - rbanffy 5y ago
      The ship would need to be very large - artificial gravity and adequate shielding for radiation and impacts would need to be provided, as well as an insane amount of redundancy and survivable abort routes. Attempting to do it with technologies we have, even with infinite funding, would be next to impossible without incurring in unacceptable risks.
- rbanffy 5y ago
  I can too, but we’ll need much better engines than what we have now to get there and back in an amount of time a crew can function. Sending 20 years worth of consumables and spares is complicated, as well as the moral questions about sending people on 20 year missions.
  - avmich 5y ago
    For some time an assumption - a rule of thumb of a sort - was that chemical rockets can get people comfortably around within Mars orbit, and to get further away we need something better. That "something" is likely not solid-phase nuclear engines, with Isp about twice as good as LOX/LH2, and probably not gas phase nuclear engines... but thermonuclear engines, which get closer to feasibility with advances in thermonuclear energy field. A thermonuclear engine could be more attainable than a thermonuclear electrical plant, and cheaper LEO access could be a big part of enabling technology. Having engines like that we may talk about much faster trips to Pluto and back.
    - rbanffy 5y ago
      > A thermonuclear engine could be more attainable than a thermonuclear electrical plant Very true. Nobody cares about breakeven for that use case.

jillesvangurp 5y ago

There are alternate sources of propellant in the solar system. Lifting it out of Earths gravity well is relatively expensive. But once you have enough of it, you could start transporting propellant from elsewhere in the solar system and start stockpiling it in strategic orbits around various objects in the solar system. Once you can do that, you'd minimize the launch weight from earth to be able to get to a LEO fueling point and use the weight savings for more interesting cargo. One industry that could emerge quickly is that of asteroid mining. There are plenty of interesting asteroids with precious metals, water, and other resources. Right now the cost of getting to these asteroids, mining them, and transporting the mined goods back is so expensive in delta-v that it has not been done yet despite several companies having been active planning for this for quite some time. So, SpaceX getting their star ship going might be a big deal.That enables us getting stuff into space and that enables us bootstrapping mining and construction activity in orbit. Plenty of science fiction books have been written on this. There's no shortage of ideas here.

BurningFrog 5y ago
My big fear with asteroid mining is that if you can move an asteroid to Earth orbit, you can also smash it into any capital city or military base on Earth. Which means that this capability is a weapon more powerful than even nuclear missiles! I don't think the world will let this be run on the honor system. So I expect space travel to become extremely tightly controlled once we get close to this tech level.
- 0xffff2 5y ago
  A relatively small number of nuclear missiles is enough to wipe out human civilization. There's no such thing as "a weapon more powerful than even nuclear missiles" in terms of Earth-focused weaponry. And we've done very little if anything to prevent countries from acquiring and maintaining nuclear missiles. If we let North Korea have nukes, what makes you think we would try to stop countries from developing space capabilities?
  - gary_0 5y ago

api 5y ago

> Earth is in a peculiar position such that the delta V of getting to orbit will also get you to anywhere else in the solar system fairly quickly. Tangent: One of my favorite answers to the Fermi paradox (not mutually exclusive with others) is that much of the life in the universe is stuck at the bottom of huge gravity wells ("super Earths") that make space flight immensely difficult and expensive, making the development of a space industry far less likely. It's a variant of the rare Earth hypothesis. Not only might Earth be rare for its stability and long-lived biosphere but also for the fact that it's large enough to hold onto a thick atmosphere and water but not so large that you can't get off it with relatively benign (compared to higher energy alternatives) chemical propellants. Increases in the mass of Earth would make space launch exponentially not linearly harder. Getting anything non-trivial off a super-Earth would probably require nuclear or hybrid (e.g. LANTR) rockets, which are problematic for ground launch in a biosphere. They'd also be a lot more costly.

Retric 5y ago

NERVA or other Nuclear thermal rockets are actually fairly low ISP compared to ION drives. A solar panel + inert gas gets you anywhere in the solar system. The real issue is what’s the point? The economics of asteroid mining gets much worse if you consider bringing vast quantities of say gold back to earth would tank the value of gold.

im3w1l 5y ago
I have been thinking about this and what I really hope we do is build a fully automated colony in space. Making it livable for humans is a huge pain in the ass, but if we restrict the scope to just sustaining robots then it becomes easier. Energy is easy: Solar panels. There is also repairs which might be trickier. Need to mine for materials and refine them into spare parts. Once you have a self-sustaining colony you could use it to assemble useful stuff. Luxury goods for terrestrial consumption. Or you could use it to build a stage-2 colony that is suitable for humans. Or maybe rockets and stuff to keep expanding into space.
- jcims 5y ago
  Pretty interesting Lex Fridman podcast episode in this area: https://youtu.be/KW8Vjs84Fxg https://youtu.be/KW8Vjs84Fxg It’s light on technical details but it’s encouraging to hear that there is progress being made in this direction.
BurningFrog 5y ago
Gold is a special case, but tanking the price of expensive metals is exactly the point of asteroid mining. If prices for nickel, iron, copper, platinum, etc were cut by 99%, it would raise human living standards ENORMOUSLY.
- skykooler 5y ago
  It would be nice if people stopped stealing catalytic converters because the plantinum, palladium etc were no longer worth the effort.
- 5y ago